DX on FX, a success, with a TC!

Over in another discussion forum, Cosmicnode asked if anyone had tried using a Nikon AF-P 70-300 VR DX lens with a Kenko TC on an FX camera, would it work, and if so, how well?!

Well, I was the one who had the combination, so I just had to try it, and it worked really well, although in low contrast/low light the AF was at time hesitant.

I also tried the Sigma 30&1.4 Art, AF-P 18-55 VR, and the 40/2.8 macro, and no issues at all.

No vignetting, focus spot on (if acquired at all).
Tord

Samples:

Surprising results for me, do you have any other examples?!

Interesting group!

Tord

I've tried c-mount lenses with poor coverage with a cheap c-mount TC coverage definitely improved as expected. Unfortunately my cheap TC was rubbish so IQ wasn't worth the effort.

No wonder here - the TC uses only the central part of an image circle

epozar wrote:

No wonder here - the TC uses only the central part of an image circle

If a 1.5x TC is taking the image from a APSC lens & spreading it to fit a FF sensor it's effectively using all the lenses image circle.

petrochemist wrote:

epozar wrote:

No wonder here - the TC uses only the central part of an image circle

If a 1.5x TC is taking the image from a APSC lens & spreading it to fit a FF sensor it's effectively using all the lenses image circle.

Never heard of a 1.5x TC, all I've used are 1.4X.
I was surprised it worked so well, considering there is an extra number of glass elements in the light path. Much better than using the same Kenko TC on a DX body, for instance!
I expected some vignetting, but I could not notice any.

Tord S Eriksson wrote:

petrochemist wrote:

epozar wrote:

No wonder here - the TC uses only the central part of an image circle

If a 1.5x TC is taking the image from a APSC lens & spreading it to fit a FF sensor it's effectively using all the lenses image circle.

Never heard of a 1.5x TC, all I've used are 1.4X.
I was surprised it worked so well, considering there is an extra number of glass elements in the light path. Much better than using the same Kenko TC on a DX body, for instance!
I expected some vignetting, but I could not notice any.

1,5x TCs are indded unusual, but the number just fiited the sensor sizes better.

I think I have seen a 1.5x in the past but 1.4x, 2x & even 3x are more common. I also have a 1.7x for that matter.

It's not unusual for the image circle of a lens to be somewhat bigger than the bare minimum for covering it's chosen sensor so a 1.4x will usually be enough to take a 1.5 crop lens up to a FF. There's likely to be a smaller proportion of Canon APSC lenses that can use this trick as their APSC is smaaler with a 1.6 crop.

In the past I've tried using a 0.7x focal reducer for using APSC lenses on MFT. the crop ratio is close to 0.7 but it didn't work for the fisheye lens I was trying. The different aspect ratio might have played a part. (The focal reducer only claims to work for FF lenses)

Tord S Eriksson wrote:

Over in another discussion forum, Cosmicnode asked if anyone had tried using a Nikon AF-P 70-300 VR DX lens with a Kenko TC on an FX camera, would it work, and if so, how well?!

I've been recommending this for a while. At Electronic Imaging 2016, I published Mixing and matching sensor format with lens coverage , which showed that the APS-C-lens-on-FF -body-via-1.5X-teleconverter trick works very well indeed.

Surprising results for me, do you have any other examples?

Here is a sample from that paper using a cheap APS-C fisheye -- arguably the type of lens one would least expect to produce good results on a teleconverter:

Opteka 6.5mm APS-C rectangular fisheye with 1.5X teleconverter on FF

Crop from the white rectangle above showing quite good quality

Aside from the fact that a 1.5X teleconverter will reduce the light by about 1 stop (sqrt(2) magnification would be precisely 1 stop), here are a few key issues:

1. The teleconverters are not very accurately labeled. Some 1.4X converters are actually magnifying more than some 1.5X (and even one marked 1.6X). However, lens coverage is usually not too tight on the native format, so there's usually enough extra coverage to be ok. The possible exception would be lenses designed for Canon's 1.6X crop not-really-APS-C cameras... but most of those still have coverage of 1.5X APS-C.

2. Many teleconverters do not properly adjust lens info electronically passed through the teleconverter. Some are simple pass-thrus that don't adjust focal length and aperture to reflect the presence of the teleconverter, which can cause various issues, the worst being incorrect IBIS correction of shake and flash exposure issues. Some teleconverters don't even implement pass thru.

3. Optical quality of teleconverters varies a lot. A lot of teleconverters are optically lousy, but some are quite good. Happily, the good ones aren't necessarily more expensive than the bad ones.

The bad news is that it can be hard to figure-out which are the good ones by #2 and #3 above without actually trying them. I've had teleconverters that were the same brand and apparently very similar model numbers, but completely different in terms of electronics and optical quality.

ProfHankD wrote:

Tord S Eriksson wrote:

Over in another discussion forum, Cosmicnode asked if anyone had tried using a Nikon AF-P 70-300 VR DX lens with a Kenko TC on an FX camera, would it work, and if so, how well?!

I've been recommending this for a while. At Electronic Imaging 2016, I published Mixing and matching sensor format with lens coverage , which showed that the APS-C-lens-on-FF -body-via-1.5X-teleconverter trick works very well indeed.

Surprising results for me, do you have any other examples?

Here is a sample from that paper using a cheap APS-C fisheye -- arguably the type of lens one would least expect to produce good results on a teleconverter:

Opteka 6.5mm APS-C rectangular fisheye with 1.5X teleconverter on FF

Crop from the white rectangle above showing quite good quality

Aside from the fact that a 1.5X teleconverter will reduce the light by about 1 stop (sqrt(2) magnification would be precisely 1 stop), here are a few key issues:

1. The teleconverters are not very accurately labeled. Some 1.4X converters are actually magnifying more than some 1.5X (and even one marked 1.6X). However, lens coverage is usually not too tight on the native format, so there's usually enough extra coverage to be ok. The possible exception would be lenses designed for Canon's 1.6X crop not-really-APS-C cameras... but most of those still have coverage of 1.5X APS-C.

2. Many teleconverters do not properly adjust lens info electronically passed through the teleconverter. Some are simple pass-thrus that don't adjust focal length and aperture to reflect the presence of the teleconverter, which can cause various issues, the worst being incorrect IBIS correction of shake and flash exposure issues. Some teleconverters don't even implement pass thru.

3. Optical quality of teleconverters varies a lot. A lot of teleconverters are optically lousy, but some are quite good. Happily, the good ones aren't necessarily more expensive than the bad ones.

The bad news is that it can be hard to figure-out which are the good ones by #2 and #3 above without actually trying them. I've had teleconverters that were the same brand and apparently very similar model numbers, but completely different in terms of electronics and optical quality.

Definitely true all of this! My Kenko works better as an FX adapter than as a TC, while the Sigma TC-1401 is impressive, but doesn't fit any of my DX lenses!

E Dinkla wrote:

Done some handheld testing with my converted Minolta MD I 200mm 4.0 and the Canon 55-250 with and without the Kenko. On an A7RII camera. with Metabones IV adapter.

Near the center, 400 and 300% view in Capture One

Near the right bottom edge , 400 and 300% view in Capture One.

I shot a church tower at 500 meters with the Kenko and that showed a good image but I am not happy with the Kenko results here. The Canon on its own is better than expected so I am not disappointed.

What this tells me is either that the converter isn't very good or that the lens is nowhere near out-resolving the A7RII sensor... or maybe both. The other possibility is camera shake, which is certainly possible, especially if the teleconverter got the focal length wrong (not adjusted).

Given that it looks better in the center and worse at the edges, the converter seems to be (mostly) at fault. Certainly, I did see a wide range of performance differences between various converters....

Thanks for the idea.  Makes perfect sense, but I would never have thought about it.  New life for my DX 10-24 on my FX body!

Tord S Eriksson wrote:

Over in another discussion forum, Cosmicnode asked if anyone had tried using a Nikon AF-P 70-300 VR DX lens with a Kenko TC on an FX camera, would it work, and if so, how well?!

The idea of using a tele converter to increase lens coverage is certainly an interesting one, but I was surprised to discover quite how old it was. As far back as the Photokina exhibition of 1970 Sigma was showing a product called the "Imagextender", a 3x converter for fitting 35mm SLR lenses (M42 or Nikon) to Bronica or Rollei 6x6cm medium format SLRs. There's a picture and a little more information here:

https://www.flickr.com/photos/38552878@N02/50542591487/in/photostream/

As far as I can remember, though, neither this or the 36-105mm f/2.8 zoom lens shown attached ever made it to market...

Heritage Cameras wrote:

Tord S Eriksson wrote:

Over in another discussion forum, Cosmicnode asked if anyone had tried using a Nikon AF-P 70-300 VR DX lens with a Kenko TC on an FX camera, would it work, and if so, how well?!

The idea of using a tele converter to increase lens coverage is certainly an interesting one, but I was surprised to discover quite how old it was. As far back as the Photokina exhibition of 1970 Sigma was showing a product called the "Imagextender", a 3x converter for fitting 35mm SLR lenses (M42 or Nikon) to Bronica or Rollei 6x6cm medium format SLRs. There's a picture and a little more information here:

https://www.flickr.com/photos/38552878@N02/50542591487/in/photostream/

As far as I can remember, though, neither this or the 36-105mm f/2.8 zoom lens shown attached ever made it to market...

Very cool! Pity it's literally just a paragraph with no other info.

I really doubted that I invented the idea in my 2016 paper , but I wasn't able to find any scholarly (or otherwise) earlier explanations of it. Not surprising that Sigma would be doing this sort of thing in that timeframe. That's back around the peak of their wildly creative collaborations with Fred Spira and Spiratone.

Nice set. The colours really pop.

Very interesting.  When I have both a TC (probably old Nikon) and a full frame body (almost certainly a Z6 II) I'll have to try the 18-55mm kit lens / TC / FTZ combo.  (It is my only DX lens.)

Thank you for the idea!

mek42 wrote:

Very interesting. When I have both a TC (probably old Nikon) and a full frame body (almost certainly a Z6 II) I'll have to try the 18-55mm kit lens / TC / FTZ combo. (It is my only DX lens.)

Thank you for the idea!

Works very well! With a Kenko, as the design of Nikon's TCs does not work!

ProfHankD wrote:

Heritage Cameras wrote:

The idea of using a tele converter to increase lens coverage is certainly an interesting one, but I was surprised to discover quite how old it was. As far back as the Photokina exhibition of 1970 Sigma was showing a product called the "Imagextender", a 3x converter for fitting 35mm SLR lenses (M42 or Nikon) to Bronica or Rollei 6x6cm medium format SLRs. There's a picture and a little more information here:

https://www.flickr.com/photos/38552878@N02/50542591487/in/photostream/

As far as I can remember, though, neither this or the 36-105mm f/2.8 zoom lens shown attached ever made it to market...

Very cool! Pity it's literally just a paragraph with no other info.

I really doubted that I invented the idea in my 2016 paper , but I wasn't able to find any scholarly (or otherwise) earlier explanations of it. Not surprising that Sigma would be doing this sort of thing in that timeframe. That's back around the peak of their wildly creative collaborations with Fred Spira and Spiratone.

Apparently another 1.4x teleconverter full frame expander is planned for this year (listed in the image, but not mentioned in the text):

https://leicarumors.com/2021/01/12/coming-soon-laowa-12-24mm-f-5-6-ultra-wide-angle-zoom-lens-for-leica-m-mount.aspx/